Echo sounding apparatus



June 26, 1945. A. McL. NICOLSON ECHO SOUNDING APPARATUS Original Filed Dec.. 16, 1958 IN V EN TOR.

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ATTORNEYS.

Patented June 26, 1945 Original application December 1 8, 1938,.Serial No.

246,180. Divided and this application February a 24, 1943, Serial No. 476,879

Claims. (Cl. 177-352) This invention relates to the art that I term "Wavemetry" and to wave detecting apparatus.

It relates more particularly to new and improved,

apparatus for, determining the direction and distance of a source of a wave echo.

application. is a division of my co-pending application for "Wave sensitive and wave front detecting devices, filed December 16, 1938, Serial No. 246,130, now abandoned.

An object of the invention is to provide new and improved apparatus for detecting wave echoesarising from the propagation of wave energy in a medium.

A further object of the invention is to provide new and improved echo sounding apparatus which responds only to an echo and not to the original wave front which produced the echo.

energy detecting means is connected to an ampli-v' fler, the output of which is impressed upon a polarization cell. The wave energy detecting means is also connected to second amplifyin means which is normally inoperative but which is rendered operative by the application of voltage from the polarization cell to the circuit. As a result. the second amplifying means is notvresponsive to the wave initially propagated through the medium, but is responsive to an echo wave front produced by the reflection of wave energy groin an object in the path of the propagated wave ront.

Referring now to detecting means comprises a conventional type crystal ill, for example, the opposite terminals of which are connected to the control grid ii and A still further object of theinyention is to provide new and improved apparatus for indicating the order inwhichecho wave energy arrives at one or more points in a-medium.

According to the invention, a detector of wave energy is provided which is normally unresponsive to the arrival of an initial wave front but is responsive to an echo wave front. The arrival of the initially propagated wave front at the detector prepares a circuit for the reception of an echo and renders it operative to indicate the arrival of the echo. v

In a further embodiment of the invention the wave detecting apparatus comprises a plurality of detectors which are so interconnected that none of them will respond to an initially propagated wave front, but the one first to receive an echo will respond, the others giving no indication of the arrival of an echo.

The invention may be better understood from the following detailed description of several representative embodiments taken in conjunction with the accompanying drawing, in which:

Figure 1 is a schematic diagram of an echo detecting circuit constructed according to-the invention. and

Figure 2 illustrates schematically a circuit for indicating, the order in which wave echoes reach spaced apart points in a medium.

For the sake of convenience, the invention will be illustrated as applied to the detection of me.- chanical vibration echoes. However, it will be readilyunderstood that the apparatus may also be usedto detect echoes of radio waves by substitutingradio receivers for the mechanical vibration detectorsemployed in the illustrative embodiments described below"; L

In the embodiment shown in Figure 1, wave the filament I: of an electronic amplifying tube II. The plate electrode of the tube I3 is connected to the positive terminal of a source of plate voltage is, the negative terminal of which is connected to one terminal of a polarization cell It, another terminal of which is connected to the filament i2 0! the tube- II. The polarization cell It may be of any conventional type and may comprise. for example. a plurality of platinum electrodes immersed in a dilute solution of sulfuric acid.- It is well known that when a cell of this typeis charged with electrical energy. it will discharge electrical energy for a certain periodof former ll, one terminal of which is connected to the control grid ii of the tube II, and the other terminal of which is connected to ground. The

secondary, winding is oi the transformer llhas one terminal connectedto the control grid 20 of a second electronic amplifying tube 2|. and another terminal connected in'series with a source of biasing voltage 22 to a variable contact 23 on a resistor 24 connected across part of the polarization cell II The filament 25 of the tube II is energized by a source of voltage 2|, one terminal of which is connected to ground and the second terminal of which is connected to a variable contact 26 on a second resistor 21 connected across another part of the polarization cell II. The plate electrode 28 of the tube. II is connected in series with a conventional type indicator is to the positive terminal of a source of plate supply III. the negative Figure 1, the wave energy terminal of which is connected to a variable contact 2| on a third resistor 22 connected across the polarization cell I 6.

In operation. the circuit components associated with the amplifier tube 2| are adjusted so that it is inoperative but, nevertheless, just at the threshold of operation. This may be done by varying the source of plate supply 20. the filament battery 26, or the grid bias battery 22 of the tube 2|, or all three of these factors, to bring the amplifying tube 2| just up to the threshold of operation. The variable contacts 22, 26a and/or 2| are then adjusted so that the arrival of a wave front at the crystal II will charge up the polarization cell sufiiciently to render the amplifier tube 2| operative to actuate the indicator 29 when an echo wave front arrives at the crystal i II. A wave front is then generated in any conventional manner and is propagated through the medium in which the crystal detector i is located. a

The arrival of the wave front at the crystal I0 causes it to generate a voltage which is impressed upon the control grid ll of the first amplifying tube l2. 'I'his charges the polarization cell is which is connected in the plate circuit of the tube i2, thereby developing diil'erent voltages across the resistors 24, 21 and 22. The voltage impressed upon the resistor 24 is positive and, therefore, reduces the grid bias applied to the control grid 2|! of the tube 2|. The positive voltage impressed across the resistor 21 is connected across the filament battery 28 so that it increases the voltage applied to the filament 25, thereby increasing the electronic emission therefrom. The voltage impressed across the resistor 22 is positive and is added to the plate supply voltage 20, thus increasing the voltage applied to the plate electrode 28 of the tube 2|. As a result of any one or all of these effects, the amplifying tube 2| is rendered operative so that when an echo wave front reflected from an object in the vicinity arrives at the crystal It, the indicator 22 will be operated.

It will be readily apparent that it is not necessary to adjust the plate, grid and filament voltages of the amplifying tube 2| for the p p e of rendering it operative to signal the arrival of an echo at the crystal III. In practice, any one of these factors will suffice to prepare the inactive tube 2| for operation. Moreover, the delayed operation of the detecting system may be further controlled by inserting other elements such as inductances 22, 22a and 24a in the plate and filament circuits of the tube 2| and in the plate circult of the tube l2. respectively. Also, instead of utilizing a polarization cell, as described above. for the purpose of rendering the circuit operative to discriminate between an original wave front and an echo wave front, a retardation relay of the type disclosed in my prior Patent No. 1,464,104 may be employed.

Figure 2 illustrates schematically detecting means for determining and signalling the order of arrival of echoes at a plurality of spaced apart points in a medium through which wave energy is propagated. In this form of the device, the thermionic retardation is produced by plate potential threshold control Of the type described above in connection with Figure 1. For the sake of simplicity, only two echo detectors are shown in the figure. However, any number of detectors may be employed as desired. Inasmuch as the detectors are substantially identical in construction, it will be necessary to describe only one in detail, corresponding parts of the second being designated by primed reference characters.

Considering now Figure 2, a conventional type crystal detector l 0 has its opposite sides connected to the control grid 24 and to the filament 25 of an electronic amplifying tube 26. The plate electrode 21 of the tube 36 is connected in series with the primary winding 38 of a transformer 29 to the positive terminal of a source of plate supply 40, the negative terminal of which is connected to ground. The secondary winding 4| of the transformer 29 is connected in an oscillator circuit 420 including an electronic tube 42. The plate electrode 42 of the tube 42 is connected to the positive terminal of a source of plate supply 44. The plate supply 44 is connected in series with an inductance 45, a polarization cell It and a choke 48 to ground. A variable tap 41 on the inductance 45 is connected in series with a variable condenser 48 to one terminal of the secondary winding 4| of the transformer 39, the other terminal of which is connected to the control grid 49 of the tube 42.

The control grid 49 of the tube 42 is also connected in series with a resistor 50 to the control grid SI of a second electronic amplifying tube 52. The resistor 50 is provided with a variable tap 52 which is connected in series with a variable source of biasing voltage 54 to the filament 55a of the tube 52 and to the polarization-cell It. The plate electrode 55 of the tube 52 is connected in series with a conventional type indicator 86 and a choke 51 to the positive terminal of a source of variable plate supply 58, the negative terminal of which is connected to the common point between the choke 46 and the polarization cell I6.

In order to determine the order in which echo wave energy reaches the crystals I0 and HI, the circuit is so designed that the detector at which the echo wave front arrives first suppresses the other detector and renders it inoperative to receive a signal. This is accomplished as shown in Figure 2 by connecting the negative side of the polarization cell l6, preferably through an inductance 59, to the control grid 34' of the tube 36'. In similar fashion, the negative side of the polarization cell I6 is connected, preferably through an inductance 59', to the control grid 24 of the tube 26.

Initially, the oscillators 42a and 42a are adjusted so as to be just about at the threshold of oscillation, and'the plate supplies 58 and 52' for the tubes 52 and 52' are adjusted to bring the tubes 52 and 52' just about to the threshold of operation. Also, the polarization cells It and I6 are so constructed that when charged by operation of the oscillators 42a and 42a, they will develop suflicient voltage to render the amplifier tubes 52 and 52' operative.

In operation, when wave energy from a, wave front initially reaches the detector III, the oscillator 42a will begin to oscillate and will charge the polarization cell IS. The voltage developed across the polarization cell I6 during the charging process is added to the plate supply voltage 58 and is suilicient to render the amplifying tube 52 operative. Accordingly, when an echo wave front arrives at the crystal III, the indicator 58 will respond. At the same time, additional voltage is developed across the polarization cell l6 by the second response of the detector l0 and is impressed as a negative voltage upon the control grid 24' of the amplifying tube 26', thereby rendering the tube 26 inoperative so that the indicator 58' cannot indicate the arrival of the echo wave front at the detector I0. Hence, if only the indicator It responds. an observer will know that the echo wave front reached the detector III first. Similar- 1y, if the echo wave front arrives at the crystal Hi before the crystal III, the indicator 88' will respond but the indicator 58 will not.

It will be apparent from the foregoing that the nvention enables echo wave fronts to be readily :liscriminated from initial wave fronts proparated through a medium containing objects which reflect wave energy. If the velocity oi the wave mergy in the medium is known, the distance of ;he reflecting object can be readily determined from the time interval elapsed between the arrival of the initial wave front at the detector and he arrival of the echo wave front at the detector. Further, by employing two or more detectors so nterconnected that the first one energized by a rave front renders the other inoperative, it is eossible to determine the direction of the source if echo wave front.

Although only single stages of amplification ire shown in the embodiments described above, )bvlously more stages may be employed if desired )1 necessary. Also, other wave detectors than :rystals may be used with good results, and pen- ;odes or other suitable tubes may be utilized in- :tead of the triodes shown.

While several specific embodiments of the iniention have been described above, the invenwion is not intended to be limited thereto. Those :mbodiments are, of course, susceptible of nunerous changes in form and detail within the scope of the appended claims.

I claim:

1. Wave detecting apparatus comprising a plurality of detectors, each having associated thererith wave sensitive means, means for amplifying "be output of said wave sensitive means, second implifying means having reduced voltage applied ihereto so as to render it normally inoperative iut at the threshold of operation, electrical inlicating means connected to be actuated by said :econd amplifying means, electrical means conlected to said first amplifying means and reniered operative upon the arrival of an original vave front at said wave sensitive means for augnenting the voltage applied to said second amilifylng means to render it operative, and elec- =rical connections between the voltage augmentng means of each of said detectors and the first lmplifying means of the other detectors to apply voltage from the voltage augmenting means if the detector first to receive an echo wave front .0 the first amplifying means of the other deectors to render them unresponsive to the arival of wave energy.

2. Wave detecting apparatus comprising a pluality of detectors, each having associated therewith wave sensitive means, means for amplifying he output of said wave sensitive means, second implifying means having reduced voltage applied hereto so as to render it normally inoperative but it the threshold of operation, electrical indicating means connected to be actuated by said second implifymg means, a polarization cell connected to aid first amplifying means to be charged thereby man the arrival of an original wave front at said vave sensitive means and adapted, when charged, augment the voltage applied to said second amlifying means to render it operative, and electrial connections between the polarization cell of :ach of said detectors and the first amplifying ieans of the other detectors to app y, a voltage om the polarization cell of the detector first to neive an echo wave front to the first amplifying means of the other detectors suited to render them unresponsive to the arrival of wave energy.

3. Wave detecting apparatus comprising a plurality of detectors, each having associated therewith wave sensitive means, means for amplifying the output of said wave sensitive means, second amplifying means including an electronic tube having reduced plate voltage applied thereto so as to render it normally inoperative but at the threshold of operation, electrical indicating means connected to said second amplifying means, a polarization cell connected to said first amplifying means and adapted to be charged thereby upon the arrival of an original wave front at said wave sensitive means for augmenting the plate voltage applied to said electronic tube to render it operative, and electrical connections between the polarization cell oi-each of said detectors and the first amplifying means of the other detectors, whereby the polarization cell of the detector first to receive an echo wave front will apply a voltage to the first amplifying means of the other detectors to render them unresponsive to the arrival of wave energy.'

4. In apparatus for determining the position of an object in a medium reflecting wave energy generated by a wave source, the combination of a plurality of devices for detecting the arrival of wave energy reflected from said object, a pinrality of means adapted to be actuated by each of said devices for indicating the arrival of a reflected signal, means associated with each of said detecting means for preventing the indicat-= ing means corresponding thereto from responding to the arrival of an original wave front from said wave source, means energized upon the arrival of an original wave front at each of the detectors for rendering the indicating means corresponding thereto operative to indicate the arrival of an echo wave front reflected from said object, and means energized by the detector-first to receive said echo wave front for rendering the other detectors unresponsive to wave energy.

5. In apparatus for determining the position of an object capable of reflecting waves generated by a wave source, the combination of a plurality of wave energy receivers, means associated with and actuated by each receiver for signalling the arrival of a wave front, said receivers being normally inoperative to actuate the signalling means corresponding thereto upon the arrival of a wave front, means responsive to the arrival of an original wave front from said wave source for raising said receivers to the threshold of operation without actuating the signalling means corresponding thereto, whereby said signalling means will be actuated upon the subsequent arrival of a reflected wave front, and means energized by the receiver first to receive a refiected wave front for rendering the other receivers inoperative to actuate their associated adapted when charged to render said amplifying means operative, and indicating means connected to respond to a received, wave when amplified by said amplifying means.

7. Echo sounding apparatus comprising wave sensitive means, a pair of wave channels connected to be actuated by said wave sensitive means, wave amplifying means in each of said channels, a polarization cell connected to be charged by operation of the wave amplifier in one of said channels and adapted when charged to supply a voltage for a limited time, means supplying the wave amplifying means in the other of said channels with a reduced voltage suited to render it normally inoperative but at the threshold of operation, said polarization cell being connected to augment the voltage supplied to said last mentioned amplifying means and adapted when charged to render the same operative, and indicating means connected to respond to a received wave when amplified by said last mentioned amplifying means.

8. Echo sounding apparatus comprising wave sensitive means, a pair of wave channels connected to be actuated by said wave sensitive means, a polarization cell in one of said channels adapted to supply a voltage for a limited time when charged by reception of a wave in said first mentioned channel, wave amplifying means in the other of said channels supplied with a reduced bias voltage suited to render it normally inoperative but at the threshold of operation, said polarization cell being connected to augment the voltage supplied to said amplifying means and adapted when charged to render said amplitying means operative, and indicating means connected to respond to a received wave when amplifled by said amplifying means.

9. Echo sounding apparatus comprising a plurality of channels each channel containing a wave sensitive means, wave amplifying means supplied with a reduced voltage suitable to render the samenormally inoperative but at the threshold of operation, a polarization cell connected to be charged ,by the reception of a wave in said channel and when charged to supply a voltage for a limited time, and an indicating means connected to respond to a received wave when amplified by said amplifying means, each of said polarization cells being connected to augment the voltage supplied to the amplifying means in its channel to render the same operative when charged by a received wave, and being connected to apply a blocking voltage to the other channels, said blocking voltages being suited to render said other channels inoperative when said cell is further charged due to the reception of an echo wave in its channel, whereby only the first channel to receive an echo wave is responsive thereto.

10. Echo sounding apparatus comprising a plurality of channels each channel containing a wave sensitive means, a first amplifying means, an oscillator and a second amplifying means, said oscillator and said second amplifying means being supplied with reduced voltage suitable to render the same normally inoperative but at the threshold of oscillation and operation, respectively, a polarization cell connected to be charged by the reception of a wave in said channel and when charged to supply a voltage for a limited time, and an indicating means connected to respond to a received wave when amplified by said second amplifying means, each of said polarization cells being connected to augment the voltage supplied to the oscillator and to the second amplifying means in its channel to render the same operative when charged by a received wave, and being connected to apply a blocking voltage to the first amplifying means in the other channels, said blocking voltages being suited to render said first amplifying means inoperative when said cell is further charged due to the reception of an echo wave in its channel, whereby only the first channel to receive an echo wave is responsive thereto.

ALEXANDER McLEAN NICOLSON. 

